Composition and co-occurrence network of the rhizosphere bacterial community of two emergent macrophytes and implications for phytoremediation

Microorganisms of the rhizosphere play essential roles in plant metabolism, growth and productivity. Phragmites australis and Triarrhena lutarioriparia are two commonly found emergent macrophytes of the Gramineae family. P. australis is widely used in constructed or artificial wetlands, whereas T. lutarioriparia is found in natural environments. Thus, these two macrophytes have different ecological functions within aquatic ecosystems. In this study we used 16S rRNA gene-based high-throughput sequencing to compare the diversity, composition and co-occurrence networks of the rhizosphere bacterial communities of each macrophyte to better understand their respective ecological functions. The results suggested that abundant taxa in the bacterial communities had a higher richness and were more diverse in the bulk soil relative to the rhizosphere compartment. The opposite pattern was found for rare bacteria in the respective microbial communities. The bacterial rhizosphere community of P. australis contained a greater proportion of genera associated with purifying water and improving water quality than that of T. lutarioriparia. P. australis also had a more complex rhizosphere bacterial network than T. lutarioriparia. These findings provide a better understanding of the ecological functions of the two macrophytes and show that adjusting plant–bacteria interactions within the macrophyte rhizosphere community is an important aspect of phytoremediation.